Method of manufacturing a coherent roebel bar coil

ABSTRACT

A one-turn stator coil for arrangement in winding slots of a rotary a.c. machine, in which the coil sides are made in the form of roebel bars, is produced by forming two hair-pin shaped bundles of strand loops, with the strand loop ends in each bundle having different radii of curvature, displacing the strand loop ends of each bundle longitudinally, with the loop end of smallest radius of curvature in one bundle facing the other strand loop ends in that bundle with its convex surface, and with the smallest strand loop end in the other bundle facing in the direction of the loop ends of the bundle with its concave surface, bending both bundles at the same distance from the nearest strand loop end to form sidewise-bent portions in all the strand loops, pushing together the curved strand loop ends of both bundles in the longitudinal direction to their original position, transposing the strands in each of the bundles successively to form a roebel bar strand disc, interfitting the two roebel bar strand discs and spreading the shanks of the resulting hairpin-shaped body to form a coil.

United States Patent Moberg Sept. 24, 1974 METHOD OF MANUFACTURING A Primary ExaminerC. W. Lanham COHERENT ROEBEL BAR COIL Assistant Examiner-Carl E. Hall [75] Inventor: Lennart Moberg, Vasteras, Sweden [73] Assignee: Allmanna Svenska Elektriska [57] ABSTRACT Aknebolaget Vasteras, Sweden A one-tum stator coil for arrangement in winding slots [22] Filed; Nov. 21, 1973 of a rotary a.c. machine, in which the coil sides are made 1n the form of roebel bars, is produced by forml PP 417,973 ing two hair-pin shaped bundles of strand loops, with the strand loop ends in each bundle having different [30] Foreign Application Priority Data radii of curvature, displacing the strand loop ends of D 8 1972 S d 16005/72 each bundle longltudinally, with the loop end of smallwe en est radius of curvature in one bundle facing the other strand loop ends in that bundle with its convex sur- [52] U.S. Cl 29/596, 29/605,3ll7gil/23l3 face and with the Smallest Strand loop end in the [51] Int Cl Hozk 15/00 other bundle facing in the direction of the loop ends [58] Field of Search 29/605 596; 310/201, 213; of the bundle wlth its concave surface, bending both 336/187, 174/33 34 bundles at the same distance from the nearest strand loop end to form sidewise-bent portions in all the strand loops, pushing together the curved strand loop [56] References Cited ends of both bundles in the longitudinal direction to UNITED STATES PATENTS their original position, transposing the strands in each v l,l44,252 6/1915 Roebel 310/213 of the bundles successively to form a roebel bar strand 1;; gucklew v disc, interfitting the two roebel bar strand discs and. annen spreading the shanks of the resulting hairpin-shaped body to form a coil.

1 Claim, 12 Drawing Figures METHOD OF MANUFACTURING A COHERENT ROEBEL BAR COIL BACKGROUND OF THE INVENTION I 1. Field of the Invention The present invention relates to a method of manu-- facturing winding coils for the stators of large a.c. rotary machines, for example for machines within the range 1 1000 MVA.

2. The Prior Art The object of a method accordingto the invention is to provide a coil in which each coil side is designed as a roebel bar, without it being necessary for that reason to make the coil sides of separate bars, which are finally connected to each other. Roebel bars are particularly advantageous in very large machines, but if the roebel bars are manufactured in an appropriate manner it may be economically justifiable to introduce roebel bars also in machines with such low power as l MVA. Roebel bars are known per se and'many recently manufactured generators have statorwindings in which the coil sides are made in the form of roebel bars. Roebel bars are described in the German Pat. No. 277,012 and in the US. Pat. No. 2,821,641, but also outside the patent literature, for example in Standard Handbook for Electrical Engineers, McGraw Hill, th Edition, Sec. 6, page 31.

In the above-mentioned generators a coil side made in the form ofa roebel bar contains a first and a second disc positioned adjacent to each other, each strand disc being shaped to alternate between the rightand the left-hand sides of the coil side and each strand being made with at least one portion bent sideways, in such a way that, in a strand disc, portions bent sideways and portions not bent sideways lie on opposite sides of an axial plane through the center'of the roebel bar. The ends of the bar are then electricallyconnected so that coils are formed.

, When manufacturing coils which are not to be made by means of roebel transposition, that is, which are not to contain any roebel bar, it is common to make the coil in the form of a so-called form coil. A conventional, untransposed one-turn coil is suitably manufactured by bending a bundle of strands into hairpin shape in a manner shown in FIG. 5 in the accompanying drawing. After this, the hairpin-shaped bundle is placed in a forming machine and the straight parts of the bundle are pulled apart in such a way that a form coil, of the same shape as in FIG. 9 but without transposition, is formed.-

Heretofore it has been regarded as'too complicated and time-consuming to manufacture a roebel coil which is not composed of two bars joined'by means of end connections, but of a plurality of strand coils, each strand coil consisting of one single, coherent and unjoined copper conductor. Such roebel coils have therefore had no commerical importance.

SUMMARY OF THE INVENTION The present invention describes a method which makes it possible to manufacture a roebel coil consisting of unjoinedstrand coils and without reduction of the accuracy, using fewer working hours than is required for conventional coils consisting of 'roebelbars which are soldered together.

According to the invention, such a roebel bar is produced by interfitting two hairpin-shaped bundles of strand loops and thereafter bending the interfitted bundles into a formed coil. In the production of each of the bundles, a plurality of hairpin-shaped parts having strand loop ends, and fitting one within the other, are displaced longitudinally with respect to each other. In one bundle, the loops of greater radius of curvature are displaced away from the loop at least radius of curvature, while in the other bundle they are displaced towards the loop of greatest radius of curvature, being bent out of the plane of and overlying the loop of lesser radius of curvature. Both bundles are then bent sidewise at a distance along the length of thebundle from the nearest loop ends. The strand loops are then displaced relative to each other in the opposite direction, until their loop ends are substantially in contacting relation with each other. The strand loops are then successively bent across each other, thereby transposing the strand loops to form a roebel bar section.

BRIEF DESCRIPTION OF THE DRAWINGS In the following the invention will be described with reference to the accompanying drawings, in which FIGS. 1 to 4 show different stages in the manufacture of a roebel bar. While FIGS. 1 to 4 illustrate a conventional roebel bar, they also illustrate how a coil side of a coil made according to the invention is put together in principle.

FIGS. 5, 6, 7, 7a, 8, 8a, 9 and 10 show different stages in a method according to the invention, FIGS. 5, 7 and 8 show strand loop bundles lying in a horizontal plane seen in the vertical direction, whereas FIGS. 7a and 8a show the strand loop bundles of FIGS. 7 and 8 seen from the side. FIG. 6 shows a cross-section along the line VIVI of FIG. 5. FIG. 10 shows a cross-section along the line XX through a coil side of the coil shown in FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 1 designates a strand for a roebel bar and 2 a sidewise-bent strand portion, the extension of which in the longitudinal direction of the strand is designated a. FIG. 2 shows one and FIG. 3 the other of two socalled strand discs which are arranged adjacent to each other in the winding slot in such a manner that the roebel bar illustrated in FIG. 4 is formed.

A method according to the invention can be started by cutting up a plurality of insulated strand bars, giving each one a length which is sufficient for a one-turn coil, that is, somewhat more than 2.5 times the length of the winding slot. The strand bars are divided up into two bundles with, for example, four strands in each bundle (as'shown in FIGS. 5-10), and each bundle is bent in the middle so that two hairpin-shaped bundles 3 are formed. Each bundle 3 has two shanks 7 which are mutually connected by means of a plurality of strand loop ends lying close to each other in FIG. 5. The radius of curvature of the outermost strand loop end 4 is several times greater than the radius of curvature of the innermost strand loop end 5. The number of adjacently placed strands is usually far greater than what has been shown in the drawing, for example twenty.

Instead of manufacturing the bundle 3 shown in FIG. 5 in the manner described above, it is possible to wind a flat coil in a known manner and cut it in the middle of a long side, thus obtaining two hairpin-shaped bundles. Each strand loop end forms a connection between two strands intended for the same coil but for different roebel bars and different winding slots of a stator for an ac machine.

In each bundle 3 of strand loops, the strand loops are then mutually displaced in the longitudinal direction, but in different ways, namely, according to FIG. 7 as far as one bundle is concerned and according to FIG. 8 as far as the other bundle is concerned. Regarding a strand loop end 5, it is evident from the drawing that the other strand loops face in the direction of the convex surface of the loop end 5 in the case shown in FIGS. 7 and 7a, but in the direction of the concave surface of the same loop end in the case shown in FIGS. 8 and 8a. In the latter case the strands must, at the same time, be bent a little near the strand loop ends in such a way that the loop ends lie in planes crossing each other.

After this the hairpin-shaped bundles 3 are treated by means of a bending tool, thus forming sidewise-bent bundle portions 6 in the hairpin-shaped bundles shown in FIG. 7 and FIG. 8 by bending simultaneously all the strands of a bundle, and in both cases at a distance b from the nearest strand loop end, that is, the loop end of the least radius of curvature in FIG. 7 and of the greatest radius of curvature in FIG. 8. Seen from the side, the sidewise-bent bundle portion 6 has the same shape as the sidewise-bent strand portion 2. After this the strand loops are pushed together within each bundle, thus giving the strand loop ends of each group the original mutual positioning, shown in FIG. 5.

In each shank of a hairpin-shaped bundle which has been subjected to a shaping according to FIG. 7 or FIG. 8, the differently bent strand parts 2 are now distributed at constant mutual distances in the axial direction, equal to the spacing of the loop ends in FIG. 7. In each of the two bundles described the transposition is then started by making, in each shank 7, a portion 2, belonging to the strand loop having the smallest radius of curvature, cross all the other strands. Similar crossings are carried out for the rest of the strands in a known manner until each of the two shanks form one strand disc according to FIG. 2.

In the other bundle the transposition is started by making, in each shank 7, one portion 2, belonging to the strand loop having the greatest radius of curvature, cross all other strands, and this is continued in a known manner until each of the two shanks of the bundle form one strand disc according to FIG. 3.

In the same way as the strand discs shown in FIGS. 2 and 3 have been combined to form the roebel bar shown in FIG. 4, the strand discs formed according to the invention are put together or interfitted to form two roebel bars which are included in a resultant hairpinshaped bundle. This is then clamped in a forming machine and subjected to formation of a form coil by spreading the parallel sides ofa one-plane coil, thus obtaining a one-turn form coil according to FIGS. 9 and 10.

I claim:

I. A method of manufacturing a one-turn stator coil (FIG. 9) intended to be arranged in winding slots of a rotary a.c. machine, the coil sides being made in the form of roebel bars (FIG. 4), wherein each coil side comprises one first (FIG. 2) and one second (FIG. 3) strand disc, each strand disc alternating between the rightand the left-hand sides of the coil side, and each strand (1) being made with at least one sidewise-bent portion (2), wherein, in a strand disc, sidewise-bent and non-sidewise-bent portions lie on opposite sides of a axial plane through the center of the roebel bar, said method including the following steps:

A. Forming first and second hairpin-shaped bundles (3) of strand loops (8), the strand loop ends in each bundle having different radii of curvature, said bundles each including two shanks and a strand loop end connecting said shanks;

B. Displacing the strand loop ends of each bundle with respect to each other in the longitudinal direction of the hairpin-shaped bundle (3) by equal distances with respect to the adjacent strand loop ends, the smallest strand loop end (5) in the first bundle (FIG. 7) facing in the direction of the other strand loop ends in. the bundle with its convex surface, in the second bundle (FIG. 8) the smallest strand loop end (5) facing in the direction of the other strand loop ends of the bundle with its concave surface;

C. Bending said first and second bundles to form sidewise-bent portions (2) in all the strand loops (8) of each bundle (3), the distance (b) between each sidewise-bent portion (2) and the smallest strand loop end in said first bundle being equal to the distance between each sidewise-bent portion (2) and'the greatest strand loop end in said second bundle;

D. Pushing together the curved strand loop ends (4,

5) of said first and second bundles in the longitudinal direction, until the axial distance between curved strand loop ends lying immediately to each other in each bundle is substantially reduced to zero;

E. In each shank of the hair-pin bundle (3) transposing the strands, thereby giving each shank (7) of the hairpin-shaped bundle (3) the form of a roebel bar strand disc;

F. Interfitting the roebel bar strand disc of said first hairpin-shaped bundle with the corresponding roebel bar strand disc of said second hairpin-shaped bundle, thus forming a resulting hairpin-shaped body containing two roebel bars;

G. Spreading the shanks of said resulting hairpinshaped body to form a form coil. 

1. A method of manufacturing a one-turn stator coil (FIG. 9) intended to be arranged in winding slots of a rotary a.c. machine, the coil sides being made in the form of roebel bars (FIG. 4), wherein each coil side comprises one first (FIG. 2) and one second (FIG. 3) strand disc, each strand disc alternating between the right- and the left-hand sides of the coil side, and each strand (1) being made with at least one sidewise-bent portion (2), wherein, in a strand disc, sidewise-bent and nonsidewise-bent portions lie on opposite sides of a axial plane through the center of the roebel bar, said method including the following steps: A. Forming first and second hairpin-shaped bundles (3) of strand loops (8), The strand loop ends in each bundle having different radii of curvature, said bundles each induding two shanks and a strand loop end connecting said shanks; B. Displacing the strand loop ends of each bundle with respect to each other in the longitudinal direction of the hairpinshaped bundle (3) by equal distances with respect to the adjacent strand loop ends, the smallest strand loop end (5) in the first bundle (FIG. 7) facing in the direction of the other strand loop ends in the bundle with its convex surface, in the second bundle (FIG. 8) the smallest strand loop end (5) facing in the direction of the other strand loop ends of the bundle with its concave surface; C. Bending said first and second bundles to form sidewise-bent portions (2) in all the strand loops (8) of each bundle (3), the distance (b) between each sidewise-bent portion (2) and the smallest strand loop end in said first bundle being equal to the distance between each sidewise-bent portion (2) and the greatest strand loop end in said second bundle; D. Pushing together the curved strand loop ends (4, 5) of said first and second bundles in the longitudinal direction, until the axial distance between curved strand loop ends lying immediately to each other in each bundle is substantially reduced to zero; E. In each shank of the hair-pin bundle (3) transposing the strands, thereby giving each shank (7) of the hairpin-shaped bundle (3) the form of a roebel bar strand disc; F. Interfitting the roebel bar strand disc of said first hairpin-shaped bundle with the corresponding roebel bar strand disc of said second hairpin-shaped bundle, thus forming a resulting hairpin-shaped body containing two roebel bars; G. Spreading the shanks of said resulting hairpin-shaped body to form a form coil. 